Contents

The Time Lords discover that the Master has stolen their secret file on the Doomsday Weapon. They grant the Doctor a temporary reprieve from his exile on Earth to deal with the crisis. He and Jo arrive on the planet Uxarieus and become enmeshed in a struggle between an agrarian colony and a powerful mining corporation.

The Time Lord High Council discuss an issue with the Doomsday Weapon - something that only they and the Master know about. They decide to use the Doctor to help them with their problem and restore his freedom for the time it takes to help them.

The Doctor is experimenting on a new dematerialisation circuit. Jo and the Brigadier try and convince him to stop. The Brigadier says that there is no sign of the Master but is called out when an agent thinks he has a trace in him. The Doctor is sceptical. Once the Brigadier leaves, the Doctor says he thinks he has fixed the dematerialisation circuit to allow him to bypass the homing control installed by the Time Lords. Jo is sceptical. For the first time, the Doctor shows Jo the inside of the TARDIS. When she says that it is bigger on the inside, the Doctor explains that it is dimensionally transcendental. All of a sudden the doors close and the TARDIS starts to dematerialise. The Doctor is confuse and says it is being operated by remote control by the Time Lords.

The Brigadier enters the lab to see the TARDIS dematerialise. He orders the Doctor back.

Jo thinks that the Doctor is playing a joke on her but he shows her the scanner to show they are outside the space-time continuum. Soon the planet Uxarieus rears into view. Jo wants to go back.

A robot is trundling around a planet's surface. As it moves off the TARDIS rematerialises.

Jo wants the Doctor to open the doors but he needs to check if the atmosphere is healthy. Once he has done that he opens the door. Seeing the alien landscape, Jo gets scared. She has always doubted the Doctor's stories of his travels through time and space. The Doctor says they should go for a quick look and then return. As they explore they are overlooked by a creature. They find track marks left by the robot and speculate that the planet must be inhabited. The Doctor wants to climb a hill to get a better vantage point. Jo is still scared but the Doctor convinced her to come. They find some dwellings atop all the hills. As they explore Jo turns to see a man pointing a rifle at them.

An inhabitant of the planet, Martin, argues with the leader, Ash, about something he saw last night. Ash is sceptical but sends his right hand man David to explore. The Doctor is brought in by the man with the rifle, Leeson. He suspects them to be mineralogists who want to use their planet for mining. The Doctor reassures them that they are just explorers. Ash wants to see their papers and when the Doctor cannot produce them, Ash says they will spend the night here and not return to their ship. Jane, Leeson's wife, shows Jo to the dining hall. The Doctor examines their crop records. Lesson goes to attack him but the Doctor disarms him with Venusian Karate. The Doctor says it looks like they have had a particularly poor harvest for some time and that they are far below sustainable levels. Ash's interest is piqued.

Outside, the creatures that observed the Doctor and Jo, steal the TARDIS.

In the dining hall, the colonists squabble about the merits of Uxarieus in relation to Earth as Jo and Jane enter. Martin is the most vocal. He prefers Earth despite the fact that it was overpopulated and oppressive when they left. David enters and takes Martin with him to look for the creatures he saw. Mary, Ash's daughter, introduces herself to Jo. She reveals that it is 2471 and that they arrived a year ago.

Leeson returns home and grumbles about the fact that there are no crops and that they shouldn't have come. Jane, his wife, said that on Earth they didn't have a room and now they have land. Lesson says that even Ash knows he's beaten. They here a noise outside and rush out. A huge lizard is outside. Jane radioes the main dome for help. She rushes for the rifle but is attacked.

Ash and the Doctor are talking about the history of the colony. The Doctor questions Ash's decision to stay but also says that there is no reason why the crops aren't growing. Mary rushes in and tells of the attack. Ash and the Doctor rush off. Jo tries to persuade the Doctor not to go but he is convinced. Jo asks Jane if they checked for signs of life before they colonised. She says that when they arrived there were no creatures.

By the time Ash and the Doctor arrive both Leeson and Jane are dead. One of the colonists report that they saw a lizard, twenty feet high, but as they approached it vanished into the darkness. The Doctor draws attention to some claw marks deep inside the dome and says that a creature that large could not have got so far into the building.

The colonists are having a meeting and want to leave. Ash insists that they can't move on. They argue that there is no food. The Doctor agrees with Ash and says that the crops are being inhibited by an unnatural source that they can track down and destroy. This begins to change the mind of some of the colonists. They decide to stay and fight. Patrol guards bring in a stranger that they found collapsed outside. He says he is from a colony a long way from here and has been wandering for months. He says that all of his friends have been killed by giant lizards.

The alien creatures that overlooked the Doctor and stole the TARDIS are examine things inside the Leeson's dome. As the Doctor and Ash enter they try and attack the Doctor but Ash calls them off. Ash explains that they don't speak but can understand what he wants. He says they are friendly now but we're quite hostile when they first arrived. Ash sends them away. The Doctor wants to examine the dome for evidence. Ash leaves him to find his own way back. As the Doctor starts collecting evidence he turns to see the giant robot entering the dome.

The robot is stopped by a uniformed man who asks the Doctor what has happened inside the dome. The Doctor explains the situation regarding the colonist. The uniformed man seems confused as he was under the impression that the planet was uninhabited. He says he is from the IMC and they have only just arrived. He says he needs to let Earth control know of the mistake. He asks the Doctor to come back with him to the ship. The Doctor refuses but the man says he has no choice. The Doctor tells the man about the death of the colonists. The man seems very concerned. They board the vehicle, programme the robot to go back to the ship of it's own accord and head off.

The colonists talk to the survivor - Norton. He says that the primitives turned on them once the lizards destroyed their infrastructure. David tells Jo that their colony's history with the primitives haven't always been perfect. David thinks this will be the wake up call that Ash needs to move on. A primitive enters. Norton loses his mind and points a gun at the creature. Ash enters and stops Norton from shooting it. David days that the only reason why there is a truce between the colonists and the primitives is because they are giving food to them that they can ill afford to. Ash and David argue. Ash leaves and Jo tells David that Ash is right.

On the way back to the ship, the Doctor notices that the TARDIS is gone.

At the IMC ship, one of the workers, Morgan, presents Dent, the captain, a survey result that states that there is enough Durilinium on the planet for a million living units on Earth and questions why it was allowed for colonisation. They see the Doctor and the other IMC worker, called Caldwell, approach on their scanner. Dent tells Morgan to follow the same story they normally do; pretend they don't know the planet is colonised and say it was all a mistake.

The Doctor is shown into a room while Caldwell fetches Dent. The Doctor switches on an entertainment console which shows Earth news detailing war.

Caldwell reports to Dent and tells of the death of the colonists. Morgan confesses that he had to kill them because they discovered him and started shooting. Caldwell says this isn't what he signed up for but Morgan says it is a means to an end. Dent shows Caldwell the report and the millions they will earn from the Durilinium. Dent goes to see the Doctor.

The news is now reporting the overpopulation of the Earth. Dent enters and introduces himself and says it is a mistake that the colonists are here due to the hostile animal life. He suggests that the colonists leave as the IMC have mineral rights. The Doctor states that Earth needs new worlds to populate not minerals that destroy other worlds. Dent disagrees. The Doctor asks after his TARDIS. Dent says he will get someone to look for it and leaves the Doctor in the room while he sorts out someone to return him to the colony. On leaving the room, Morgan tells Dent that Caldwell is looking for the Doctor's TARDIS. Dent tells Morgan that the Doctor is not a colonist and that he may be from Earth's government checking up on them. Dent says that Morgan is to return him to the dome and kill him, making it look like he is another victim of the monster. Caldwell enters and says that there is no trace of the TARDIS.

The Doctor is trying to find his way out of the room when Morgan enters. The Doctor asks why he was locked in and why he keeps being passed from person to person. Morgan says that he is to take the Doctor back to the colony and organise a meeting between Dent and the leader of the colonists. On the way Morgan asks if the Doctor can show him the dome where the colonists were killed.

On the way to the dome they are stopped by primitives. Morgan tries to shoot them but the Doctor stops them. They attack and the Doctor uses one of their spears and Venusian Karate to disarm them, before getting in the vehicle and driving off.

Mary and Jo make dinner. Jo asks Ash about the Doctor. He says if he isn't back by the time that David comes back from showing Norton around then he will send David out to get him. Jo says that Norton has made a very quick recovery.

David shows Norton the power supply junction box manned by Jim Holden and a primitive. Here the power from the ship's nuclear generator is tapped and sent out around the colony. They return to the dining quarters and chat with Jo and Mary. Norton says that his colony was better equipped than theirs but it did them no good. Mary tells David that Ash wanted to see him. David heads off and Norton goes to lay down.

Holden has fixed the power supply. Norton enters and strikes the primitive over the head with a spanner before attacking and killing Holden.

Mary enters and tells Ash that dinner is ready. All of the power goes out. Norton enters and urgently fetches Ash. He takes Ash to the power supply junction box and shows him the scene. Norton says that the primitive killed Holden and then attacked him. He says that he killed the primitive in self defence. Ash sees that the relay circuits have been destroyed and that the colony will come to a standstill as they have no one to fix it.

Dent says a message to IMC headquarters that there is tonnes of Durilinium and an issue with colonists. Caldwell enters and asks what is to be done with the colonists. Dent says that they will decide to leave. Caldwell realises what is going on and realises that the Doctor is in danger. He wants to go after them but Dent blocks him. Dent says that he can kill him there and then and say he struck him. Dent says that the death of the Doctor is a small price to pay for the Durilinium. Caldwell is unsure but Dent says that he knows the debt that Caldwell is in and that if he ruins his plan he will ensure he never works again.

The Doctor and Morgan arrive at the dome. The Doctor shows Morgan the marks and says that he thinks it is a fake. Morgan shows the Doctor a robot that enters with huge claws on his arms. He says that it looks like the monster is going to claim another victim.

Morgan threatens the Doctor with his gun. The Doctor points out that any gunshot in his corpse will ruin Morgan's story. Morgan hesitates and the Doctor disarms him. Morgan escapes. The robot looms in on the Doctor who manages to reach the remote control and disable the robot.

The colony is in chaos due to the limited power. Jo is worried about the Doctor. Ash initially says that he has more important things to worry about but then says he will send someone out to look for him. They hear the noise of an approaching spaceship.

The IMC ship is landing next to the colony. Dent leaves to make contact with the colonists.

Dent feigns surprise at the existence of the colony. Dent says he will send for an adjudicator to decide who the planet belongs to. Ash knows this will take years and will allow the IMC to mine the planet in the meantime. The Doctor enters and tells the colonists exactly what the IMC have been doing and that he looks forward to telling that to the adjudicator. Dent leaves. The Doctor says the creatures that have been plaguing the colonists was only optical trickery plus a robot with claws. Ash tells the Doctor about the power issues. The Doctor is more worried about the loss of his TARDIS but relents. Jo is concerned about the whereabouts of the TARDIS but the Doctor calms her down before he leaves. Norton stirs up dissent about the Doctor's story. Jo sticks up for him and says they could go and look through the IMC spaceship for proof.

Dent is furious at Morgan for ruining their plan. Norton radioes Dent and warns him of David and Jo's plan.

David and Jo sneak aboard the ship and avoid the robots and the IMC workers until they reach the Communication Deck. As soon as they enter they ambushed by Dent and his guards.

The Doctor has fixed the power permanently. Ash says that Norton had been trying to fix the power with no success. The Doctor notes that it looks like someone has been trying to destroy the power source instead. Mary enters and says that Dent has sent for the Doctor.

Dent tells the Doctor that Jo is under arrest for robbery. The Doctor asks what Dent wants and Dent says he wants the Doctor to remain silent when the adjudicator arrives. He refuses. The Doctor asks where Jo is. Dent explains she is placed by an explosive charge used for surveying.

An IMC guard, Allen, attaches Jo and David to the explosive. David tries to break through but Allen advises him that that isn't a good idea.

The Doctor tells Ash about the situation. Everything that Ash suggests puts Jo in more danger.

David says that there is grease on the casing of the explosive. David uses some of the grease to ease Jo's hands from the manacles. David wants Jo to go to the dome to warn Ash but she insists on freeing David. She tries to break through the chains but it triggers an alarm on the bomb.

This noise registers in the IMC ship. Dent checks with Allen.

David is freed but as they go to escape he is shot and wounded by Allen who grabs Jo. Allen reports to Dent who sends guards after David.

David evades some guards and heads towards the main dome but is discovered by two more guards who shoot at him. He runs but comes face to face with another guard. As the two original guards approach they hear a gun shot. The worker tells them that he sorted out their problem. As the guards leave, the worker is revealed to be Caldwell. He tells David that he can stop playing dead now. Caldwell helps David into his shelter where he frees him and checks him over and gives him an injection. David tells Caldwell of the situation with Jo. Caldwell advises David that the colonists should just leave as the IMC always win.

Ash is organising a search for Jo when David enters. He tells them that they were being kept in the primitive ruins but Jo would have been moved by now. David's plan is to mount an attack on the IMC spaceship, get them to surrender, release Jo and make them leave. Ash argues and the Doctor says that it is a bad idea but David leaves to organise the colonists. The Doctor asks David for directions to where Caldwell is.

The Doctor arrives at Caldwell's base. Caldwell says that Dent is just trying to scare the colonists. The Doctor warns Caldwell of the attack but says it can be stopped if Jo is freed. Caldwell agrees to help but warns that if the colonists attack it will not be a battle but a slaughter.

Morgan is informed by radio that the adjudicator is nearby. He passes this news to Dent. Caldwell enters and orders that Jo is brought back or he stops surveying - something he will have to explain to head office. Dent relents but says that Caldwell has committed professional suicide.

As Allen frees Jo, the primitives enter. Allen shoots one but is killed by a tomahawk. They kidnap Jo.

The Doctor is dissuading Ash from attacking. Ash is unmoved. The Doctor tips Ash off about his suspicions regarding Norton and then says he has a better plan for gaining access to the ship.

Mary is sent forward to engage the guards in conversation whilst the Doctor and David sneak up behind them. They knock them out.

Dent tries to contact Allen but there is no response. Caldwell thinks it is a stalling tactic.

The Doctor and David enter the ship in the uniform of the disarmed guards. Guards are soon alerted and an alarm is raised. They take an IMC worker hostage and demand they are taken to the control room. As soon as they enter the Doctor demands to know where Jo is. Dent says she has vanished. The Doctor leaves David in charge so he can go and look for her. Dent warns David that he is committing an act of piracy. David orders Dent to surrender.

The Doctor and Ash go to the primitive ruins and discover Allen dead at the hands of the primitives. The Doctor says they must be turning against humanity. Ash suggests they have taken Jo to their city but warns the Doctor that no one has ever gone to the primitive's city and survived.

The Doctor says he is to go after Jo. Ash dissuades him and says that they have been known to ransom humans for food. The Doctor says he will go and make that offer to them. As he leaves the hear the noise of a ship. The adjudicator has landed.

Dent says that the adjudicator will not look kindly on the colonists actions of seizing the ship. David finds the projector that displayed the lizard alongside the claw that made the scratches. He says he will use this as evidence.

Ash rushes to talk to the adjudicator by radio. He is brusque and says he wants to meet both parties at the same time. Ash is worried that they know look like the aggressors.

Jo is summoned to the leader of the Primitives. He is smaller than the rest, white and horrific looking. She screams.

Ash contacts David to tell him of the adjudicator's demands. David agrees to free the IMC workers. Alec Leeson - the brother of the killed colonists - wants to kill the IMC workers. Morgan turns on Dent and says it was all his fault and he has proof in a secret compartment under the desk. David asks to show him but it is a trick and Morgan grabs a gun and holds them up.

The Doctor finds the entrance to the Primitive City and finds he is surrounded by Primitives. He offers them food in exchange for Jo. He is led in.

The adjudicator meets with Ash and Mary. As he enters the dome, Ash panics as to the whereabouts of David and the IMC workers. As the adjudicator turns, he is revealed to be the Master.

Jo is pleased to see the Doctor. She tells him of the leader of the Primitives and the Doctor speculates as to whether they are two races. The Doctor tells Jo of the plan to free her. Jo says that the Primitives are descendants of a highly advanced civilisation and shows him a visual history painted on the walls that shows buildings, cities, machines and flight. However as the history continues it shows ruin and death caused by some kind of catastrophe. The last slide sees a man forced through some kind of hatch in a form of human sacrifice. The costume enters and walks up closely to the two humans. The Doctor speculates that it is almost blind. The Doctor makes the offer of food. The creature consults the pain where the sacrifice is shown, points to it and then points to the Doctor before they all leave.

Ash presents the facts to the Master. The Master asks if there is any evidence but David has to admit that it has been destroyed. Ash does not tell the Master about the killings. The Master calls the IMC to make their claim.

A primitive enters. The Doctor distracts him with a magic trick before knocking him out. They escape and sneak past the leader they saw before. They discover there is a number of these white half-blind Primitives operating alongside the taller green ones. The white Primitives find the primitive unconscious and send the guards after the Doctor and Jo. They are soon surrounded by a mixture of white and green Primitives and led into a central room. One of the white Primitives opens a hatch which leads to a blinding light. The Doctor suggests it is some kind of reactor. A panel opens in the wall and a tiny version of the white Primitives emerges from behind sat on a throne. It tells the Doctor and Jo that all intruders are forbidden here under punishment of death. The Doctor says that if they are a civilised society they should not kill. The creature states it is their law but the Doctor says that with law must come justice. The creature senses that the Doctor is a being of superior intelligence so says that he will let him and his friend go but warns him that if he returns he will be destroyed. As the Doctor and Jo leave, the creature returns back into the wall. The Doctor and Jo leave the city. The Doctor speculates whether they are dealing with three races or three mutations of the same race. Jo says they do not have time for philosophy and need to return to the main dome.

The Master has heard the IMC's statement and is weighing up his findings. He explains that an error occurred due to a faulty computer which allocated both parties the planet so he has to judge each case on its merits. The Doctor and Jo enter. All parties recognise each other. The Master says he needs time to consider his decision and withdraws, followed by the Doctor and Jo. The Doctor asks why he is impersonating the adjudicator- the Master dodges the question. The Doctor threatens to expose him as an imposter but the Master says his documents are forged so perfectly nobody would believe him. The Master questions if the Doctor has any credentials. When the Doctor admits he doesn't the Master says he could send him back to Earth as a prisoner unless he keeps quiet. The Master returns and sums up the case in favour of the IMC. He says the colonists are failing but the IMC can contribute to the issues on Earth.

Later the IMC workers are getting drunk to celebrate. Caldwell asks what happens if the colonists refuse to leave. Dent says they will be rebels and that Morgan knows how to deal with rebels.

Ash suggests they appeal but David says that is a lengthily process by which time the planet will be decimated. David wants to capture and disarm the IMC workers and force them to leave. Ash says this will make them outlaws but David says they could form a republic independent of Earth. Ash forbids and says he wants to carry out his protest by legal methods. David says he has no intention of changing his mind. Ash goes to the Doctor and tells him of David's intentions before he goes off to talk to the Master. Jo asks why the Doctor doesn't tell Ash that the Master is not the real adjudicator. The Doctor explains that he wants to figure out why the Master is here first. He follows Ash to listen to his conversation with the Master.

The IMC ship receives a message from the adjudicator but the reception is poor. The message is that all parties must meet to ratify the decision. The message is really from David who is planning an ambush.

The Doctor eavesdrops on Ash and the Master's conversation. The Master says the appeal will fail unless of special circumstances like a discovery that the site has significant historical interests. Ash Mentions the ruins of the Primitives. The Master asks for more information.

The colonists spread out and discover that Norton is missing. Alec goes to look for him.

Norton tries to contact the IMC workers but is interrupted by Alec. He sees the radio and the two fight. Alex is shot but the radio is destroyed. Norton returns to the colonists and takes his positions. As the IMC workers enter, Norton screams out that it is a trap. David kills Norton and a fire fight ensues with deaths on both sides. The Doctor runs forward with every intention of stopping the fight but the Master stops him. He pulls out a gun and tells the Doctor and Jo that they are about to fall victim to stray bullets from the gun fight.

David captures Dent and forces the surrender of the IMC workers who are to be kept under guard. Ash rails against David for his actions. David says he wants the Master to be accompanied back to his ship to go back to Earth. The Master says that they need him to adjudicate with Earth. He goes on to explain how impressed he is with the colonists and their plea that the planet has historical interest. He wishes to see the Primitive city. The Doctor tells Ash that he is not the real adjudicator. The Master says that they can check his credentials with Earth and then asks for the Doctor's credentials before he excuses himself with Ash saying they shouldn't trust the Doctor with their secrets. The Doctor tells Jo that they need evidence on the Master and says they should go and look in his TARDIS. The Doctor says that he still has the key that he stole when the Master first came to Earth.

David takes the IMC workers back to their ship and orders them to leave the planet and that the adjudicator is now on their side. When left alone Dent orders the adjudicator's details should be checked with Earth. David recontacts the ship and says they have placed explosives under the ship that will go off if they do not leave immediately. Morgan thinks that they are bluffing but Dent is spooked.

The Doctor and Jo enter the Master's TARDIS - first circumnavigating an alarm beam.

The IMC ship hovers over Uxarieus. They receive a message from Earth with a picture of the real adjudicator. Dent orders they go back into landing orbit.

The Doctor finds a mineralogical survey of Uxuarieus and a range of other planets; the Master must be looking for something. Jo also finds the real adjudicator's credentials. The Doctor wants to find out why the Master is so bothered with this planet.

The Master checks a device that shows footage inside his TARDIS and sees the Doctor and Jo snooping around. He is interrupted by Ash. He hides the device but presses a button on it.

A gas is released in the TARDIS and the door is closed. Both the Doctor and Jo drop to the ground.

Ash shows the Master the chartered areas around the Primitive city but says that the Doctor is the first person to go there and return. The Master says he will go and get the Doctor.

The IMC ship lands on the other side of a range of hills. They intend to go and and surprise the colonists. Caldwell is unsure.

The Master wakes the Doctor and says that he needs him as a guide. He intends on using Jo as a hostage.

David is concerned that he can find neither the Master nor the Doctor. David implores Ash to hand the IMC's guns around to the colonists but Ash says that there is no need. David disagrees.

The guards around the main dome are disarmed by IMC guards and the main dome is infiltrated. They storm Ash's room and take him hostage. They take their guns back.

David finds the guards unconscious and a fire fight ensues. Ash is led into the fracas as a hostage of the IMC. The colonists surrender. They are imprisoned and Dent says that Ash and David need to be kept safe in preparation for trial.

The Master has stored the Doctor and Jo in cubicles overnight. He frees the Doctor and shows him a device where he can release lethal gas into Jo's cubicle remotely. As he leads the Doctor out, the Doctor drops the key on the ground.

Dent opens the trial of Ash and David. They are being tried for destroying property and equipment belonging to the Interplanetary Mining Corporation, assault and murder of IMC personnel, trespass on a planet lawfully allocated to IMC, and armed rebellion against the lawful representatives of the Earth's government. David is furious and says that he wished he had killed the IMC workers when he had the chance. Ash asks why the adjudicator is not present. Dent says he doesn't need the adjudicator as he is now the legal ruler of Uxarieus. He states that three of the crimes they have committed are punishable by life imprisonment and the other two by death. He passes judgement that their executions are to be suspended on the proviso that they leave the planet immediately. Ash says that the ship will not survive takeoff but Dent is unmoved.

The Primitives see the Master and the Doctor approaching the city by car. They are stopped by an irrigation pipe in the road. As the Doctor goes to move it the Primitives cause an avalanche which knocks the car over. The Doctor warns the Master that he is to be attacked by a Primitive. The Master kills it. They continue their approach to the city on foot.

Mary radioes Dent's orders to the rest of the colonists. Caldwell says that the ship is not in the best condition. Mary begs Caldwell to show mercy.

Morgan can't find the Master and that the hatches on his ship are sealed. Dent tells Morgan to take Caldwell to the ship and use explosives if needs be. Caldwell tells Dent that the colonists' ship could explode on the ground. Dent orders all IMC workers inside on blastoff.

The Doctor leads the Master to the entrance but doesn't know how to get in. The Master threatens him.

Caldwell and Morgan give up and are about to blow the door off when they find the key. They go in and find Jo but they have triggered the alarm.

The Doctor uses Venusian Karate to disarm the Master but their altercation is broken up by the Primitives who lead them into the city.

Morgan and Caldwell manage to free Jo who tells them of the Master's plans and where he has gone.

The Doctor and the Master are led to where the Doctor was held previously. The Master offers to help the Primitives but they leave without heeding him. The Doctor shows the Master the pictorial history.

Jo has explained to Caldwell the history of the Master but Dent interrupts and says that Jo is to join the colonists on their ship. Caldwell seems to enforce the message but hides Jo under tarpaulin in a buggy.

The Master is impressed with the pictorial history. He explains that this planet used to be the centre of a great civilisation of a super race of which the small white creatures used to be a ruling race. This super race developed a Doomsday weapon but ended up becoming priests that worshipped technology and couldn't bear to be destroyed by it. The Doctor explains that they are to be sacrificed to this technology unless they do something. The Master says he wants to use this weapon to hold the galaxy to ransom. As the Primitives enter, the Master shows the Doctor a gas mask and canister. As soon as the Primitives enter, he deploys it and he and the Doctor escape.

Morgan checks the list of names aboard the colonists' ship and questions why David's name is checked off. Mary insists he is aboard. Ash says he is ready to go. He tries one last time to convinced Dent. He says he is the only qualified pilot and asks what Dent would do if he refused to leave. Dent says that he would guard the door and kill anyone that left the ship. As Ash heads off Dent orders a guard to keep,watch of the ship at all times.

The Doctor and the Master are looking for the Doomsday Weapon. The Master thinks they are nearly there.

Morgan sees Ash and Mary aboard the ship.

Dent is turning the colonist base into an IMC base. Unbeknownst to him, David is watching over him.

A security guard watches the ship. Dent checks on the guard by radio. David sneaks up and knocks the guard out after a prolonged fight.

Dent and Morgan are restless as to why the ship hasn't taken off. They get the colonists' ship on video link. Ash explains their is an electrical fault regarding their life support. He says it will soon be fixed and that the countdown will begin in a few moments.

Caldwell and Jo come across the Doctor and the Master's upturned buggy. They watch as the Colonist' ship takes off and explodes. Caldwell is emotional.

The Master and the Doctor have arrived at the heart of the Doomsday Weapon - a weapon that stretches miles around them. The Master says that the weapon has the capacity to blow up the Sun - in fact its prototype created the Crab Nebula.

Caldwell and Jo arrive at the entrance to the Primitive City but can't get in. They are at the point of giving up when the door opens. A Primitive exits as Caldwell hides. As it approaches Jo, Caldwell jumps out and knocks him over. He holds the door opens and the two go in.

The Master says that the Doctor could come in with him, saying that the Doctor could reign benevolently and end war, suffering and disease. The Doctor turns him down and says that absolute power is evil. The Master tempts him again and says that he is offering a half share in the universe.

Caldwell and Jo are looking for the Doctor and the Master but Jo has to admit she is lost.

Dent wants to know the whereabouts of Caldwell and says that Morgan should go and look for him. Morgan is worried about the trouble from Earth after the death of the colonists. Dent says he has fabricated a document saying that the colonists refused help with their ship.

The Master begs the Doctor to see reason but he refuses. The Master tries to turn him against the Time Lords but the Doctor says he would rather see the universe rather than rule it. The Master is infuriated and goes to kill him but the leader of the Primitives emerges from the wall and demands to know why the Doctor has returned. The Master says he has come to offer a plan that will restore the city and planet to its former glory. The Doctor begs the leader not to listen. The Master says that the planet oils be the centre of a mighty empire. The Doctor asks if the weapon has ever brought any good to the planet. The leader says that it was the radiation from the weapon that polluted the soil of their planet and led to their downfall. The Doctor says that that is why the weapon should be destroyed. The Master begs the leader and says they could be gods. The leader says the Master shouldn't be a god. The Master tries to kill the leader but he uses his telekinesis to remove the weapon from his hands. The leader tells the Doctor that there is a self destruction mechanism on the weapon and asks the Doctor to activate it. The Doctor operates the lever with the help of the leader. The leader tells the Doctor to leave at once or he will be destroyed with the city. The Doctor runs while the city starts to crumble. As he leaves the Doctor finds Jo and Caldwell. As they head off they find the Master and ask for his map to help them leave. He refuses but Caldwell pulls his gun and forces him. They leave just as the city explodes. As soon as they leave the Master tries to disarm Caldwell but fails. Soon all four of them are surrounded by IMC workers. Morgan orders Caldwell away from the other three. The Master tries to take control of the situation but is rejected by Morgan as an imposter. The Master then sides with the Doctor. Morgan goes to kill them but Caldwell tells him to stop. Morgan turns to him and says that he is lucky to not be dying too. This momentary distraction allows a group of colonists to surprise the IMC workers. As a fire fight ensues, the Master steals a buggy and flees. David forces the surviving IMC workers to surrender. Jo realises that the Master has left. They take a buggy and pursue him.

The Master arrives in his TARDIS and sees the Doctor and Jo pursue him on the scanner.

As the Doctor and Jo arrive they see the Master's TARDIS dematerialise.

Later, the Doctor explains to David that now the weapon is gone the crops will grow. Jo asks how the colonists survive. David explains that, once the guard was knocked out, the rest of the colonists left apart from Ash who sacrificed himself to create a decoy to lull the IMC workers into a false sense of security. The colonists interrupt to say they have found the Doctor's TARDIS in one of the Primitive dwellings. Caldwell is now working with the colonists and tells them that a real adjudicator is on his way. As they talk the TARDIS dematerialises behind them.

The TARDIS returns on Earth the exact moment it left. The Brigadier sarcastically congratulates the Doctor on his short trip. Jo tries to explain but the Doctor says there is no point as the Brigadier wouldn't understand.

Director Michael Briant voiced the commentary accompanying a propaganda film watched by the Doctor on the IMC spaceship in episode two. This part was originally intended for Pat Gorman, who was credited on episodes one and two as "Primitive and Voice".

The Radio Times programme listing for episode one was accompanied by a continuation of the comic strip adaptation (see Comic Strip Adaptation below) in the form of three additional black and white illustrations not included in the strip itself: the first showed the Doctor looking over a rise, with Jo in the background asking "What is it?"; the second depicted the colonists' dome and spaceship; and the third was the shadow of a mysterious humanoid figure behind the Doctor and Jo. The accompanying caption read "A new adventure for Dr. Who: 6.10".

Right after the lights to the colony go out following Norton's attack on Jim Holden and a primitive, Mary Ashe says to her father, "Don't worry, Jim'll fix it!" By coincidence, this line unintentionally name drops the title the BBC show Jim'll Fix It, which did not premiere until 1975. However, it later featured Tom Baker and Peter Cushing, who played the Fourth Doctor and Dr. Who respectively, and also devised the fourth-wall-breaking short A Fix with Sontarans.

Pat Gorman was credited as "Primitive and Voice" on episodes one and two, but did not provide the voice. He was credited as "Primitive" on episodes four and six. In Radio Times, he was billed only as "Primitive".

Roger Delgado was credited as "Master" on episode four and "The Master" on episodes five and six.

In episode two, the monitor screen on board the IMC spaceship turns bright blue in every close up.

In episode three, as Winton, while pursued by IMC guards, falls at Caldwell's feet, seagulls can be heard.

In the last scene of episode six, after the Brigadier has repeated his "Come back at once!" line, the shadow of a crew member can be seen across his front.

In episode four, when the diminutive leader of the Primitives, the Guardian, exits from the wall, its puppeteer, particularly his hand, is visible.

Briant admits in the commentary track for the DVD release and in the accompanying documentary IMC Needs You! that the reason the TARDIS pops in and out of sight in episodes one and six instead of fading out is that he just didn't know it was supposed to.

In episode one, when the Doctor and Jo are in the TARDIS, Jo is wearing a pink shirt with black stripes. Once they left the TARDIS after landing on the planet, however, she is wearing a grey shirt with black stripes. When held hostage, she is wearing the pink shirt again.

In episode three, Winton's handcuffs open before Caldwell has even touched them.

This is the first time that the TARDIS travels to another planet since the Doctor's exile began. (TV: The War Games) It is only able to do so because it is under Time Lords control.

From the Brigadier's perspective, the Doctor and Jo were only away from UNIT headquarters for seconds. Rose Tyler later admonished her mother that the TARDIS is "a time machine. I could go travelling around suns and planets and all the way out to the end of the universe, and by the time I get back, ten seconds would've passed. Just ten seconds." (TV: World War Three)

The Doctor and Jo gain entry to the Master's TARDIS using the key the Doctor previously obtained. (TV: Terror of the Autons)

This is the first time Jo Grant sees the interior of the Doctor's TARDIS. Though having been the Doctor's companion for some time, she reveals that she never really believed that the Doctor could travel in time and space. (TV: Terror of the Autons)

The opening scenes of episode one were adapted as a three-page comic strip — with the first two pages in colour, and the third in black and white — illustrated by Frank Bellamy in Radio Times (cover dated: 10-16 April 1971), which accompanied a short article by Russell Miller entitled Dr. Who zooms off into time again. The opening narrative panel for the strip referred to the previous adventure, The Claws of Axos, by its working title Vampire from Space and read, "In his last adventure, Vampire from Space, Dr. Who used his space/time machine the Tardis to save Earth from the alien parasite creature Axos by forcing it into a time-loop. But Dr. Who is afraid that the Master, who sent Axos to destroy Earth, has escaped and will fight again... now read on." The closing narrative panel read, "Who are these strange humanoid creature [i.e. the Primitives]? Is it their machine whose tracks Dr. Who has discovered — or are other forms of intelligent life on this planet? And why have the Time Lords sent the Doctor here? Don't miss the first thrilling episode of his new adventure: Saturday 6.10 BBC1 Colour."

Contrary to common belief, season 10 kicked off in the last week of December 1972 — not in 1973, as would be expected. Season 10 actually began nine years after season 1 started. In fact, The Three Doctors began nine years to the week after The Daleks first aired.

For the purposes of this list, "Series 4" is considered to be the production series 4, which ran all the way from Time Crash to The End of Time.

The years seen in this section may seem decidedly "off". Remember, however, that this list only gives the first year in which an episode from a series was broadcast. David Tennant, unusual amongst other Doctors, began and ended on special episodes, not regular ones. Thus, his series actually begin in 2005, 2006 and 2007 — not 2006, 2007 and 2008 as is commonly thought.